Knives with retractable blades have long been known. See, for example, U.S. Pat. No. 845,792 issued Mar. 5, 1907 to Luther E. Jenkins; U.S. Pat. No. 2,640,260 issued June 2, 1953 to Clarence E. Taylor et al; and U.S. Pat. No. 3,025,598 issued Mar. 20, 1962 to Warren I. Nissen. Each of these knives has a disadvantage which is overcome by the knife of the present invention. In Jenkins the knife is fastened to one end of a spring coiled within the handle and when the spring is activated it projects the knife blade outwardly beyond one end of the handle. The spring contracts when the knife blade is pushed back into the handle. Difficulty has been encountered with the Jenkins knife because the coil spring is easily subject to becoming fouled, rendering the knife useless.
Taylor et al discloses a retractable pocket knife which eliminates the coiled spring of Jenkins and the consequent danger of the spring becoming fouled. Taylor et al does not have any means for positively locking the knife blade in either open or closed position. Instead, frictional resistance is provided by the pressure exerted by a spring pressed actuating button to frictionally retain the knife blade in a desired position. This is dangerous because of the possibility that the blade may be unintentionally dislodged if jammed against something.
U.S. Pat. No. 3,025,598 to Nissen discloses a knife with a retractable blade utilizing a carrier and a guide within the handle to selectively move the blade between open and closed position. In Nissen it is the carrier which is manipulated to move the blade which is more cumbersome and less reliable than the operator being able to grasp the blade and move it as desired between open and closed position as in the present invention.